1. Field
The present invention relates generally to communications, and more specifically, to the transmission of packetized data over wireless communication systems.
2. Background
The field of wireless communications has many applications including, e.g., cordless telephones, paging, wireless local loops, personal digital assistants (PDAs), Internet telephony, and satellite communication systems. A particularly important application is cellular telephone systems for mobile subscribers. As used herein, the term “cellular” system encompasses both cellular and personal communications services (PCS) frequencies, or any other frequencies upon which wireless telephony networks may operate. Various over-the-air interfaces have been developed for such cellular telephone systems including, e.g., frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). In connection therewith, various domestic and international standards have been established including, e.g., Advanced Mobile Phone Service (AMPS), Global System for Mobile (GSM), and Interim Standard 95 (IS-95). IS-95 and its derivatives, IS-95A, IS-95B, ANSI J-STD-008 (often referred to collectively herein as IS-95), and proposed high-data-rate systems are promulgated by the Telecommunication Industry Association (TIA) and other well known standards bodies.
Cellular telephone systems configured in accordance with the use of the IS-95 standard employ CDMA signal processing techniques to provide highly efficient and robust cellular telephone service. Exemplary cellular telephone systems configured substantially in accordance with the use of the IS-95 standard are described in U.S. Pat. Nos. 5,103,459 and 4,901,307, which are assigned to the assignee of the present invention and incorporated by reference herein. The IS-95 standard subsequently evolved into “3G” systems, such as cdma2000 and WCDMA, which provide more capacity and high speed packet data services. Two variations of cdma2000 are presented by the documents IS-2000 (cdma2000 1xRTT) and IS-856 (cdma2000 1xEV-DO), which are issued by TIA. The cdma2000 1xRTT communication system offers a peak data rate of 153 kbps. The cdma2000 1xEV-DO communication system defines a set of data rates, ranging from 38.4 kbps to 2.4 Mbps, at which an access point (AP) may send data to a subscriber station (access terminal, AT). Because the AP is analogous to a base station, the terminology with respect to cells and sectors is the same as with respect to voice systems. The WCDMA standard is embodied in 3rd Generation Partnership Project “3GPP”, Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214.
Given the growing demand for wireless data applications, the need for very efficient wireless data communication systems has become increasingly significant. One such wireless data application is the transmission of data packets that originate or terminate at packet-switching networks. Various protocols exist for transmitting packetized traffic over packet-switching networks so that information arrives at its intended destination. One such protocol is “The Internet Protocol,” Request for Comment (RFC) 791 (September, 1981). The Internet Protocol (IP) breaks up messages into packets, routes the packets from a sender to a destination, and reassembles the packets into the original messages at the destination. The IP protocol requires that each data packet begins with an IP header containing source and destination address fields that uniquely identifies host and destination computers. Another protocol is the Point-to-Point Protocol (PPP), promulgated in RFC 1661 and RFC 1662 (both published in July 1994), which is an encapsulation protocol for transporting IP traffic over point-to-point links. Yet another protocol is the IP Mobility Support, promulgated in RFC 2002 (October 1996), which is a protocol that provides for transparent routing of IP datagrams to mobile nodes.
Hence, the transmission of data packets from the IP network over a wireless communication network or from the wireless communication network over the IP network can be accomplished by adherence to a set of protocols, referred to as a protocol stack. A wireless communication device may be the origination or the destination of the IP packet, or alternatively, the wireless communication device may be a transparent link to an electronic device. In either case, payload information is broken into packets wherein header information is added to each packet. The IP header sits on top of the PPP layer, which sits on the RLP layer, which sits on top of the physical layer. The RLP layer is the Radio Link Protocol layer, which is responsible for retransmitting packets when a transmission error occurs. The packets are transported over the air to a packet data service node (PDSN) via an Access Point (AP), whereupon the packet is subsequently sent over the IP network. Alternatively, IP packets are transmitted over the IP network to a PDSN, from a PDSN to an AP, and then over-the-air to a wireless communication device. The wireless communication device is also referred to as an Access Terminal (AT) herein.
Various connectivity problems arise due to the mobility of wireless communication devices. Some of these problems arise when a mobile wireless communication device moves from the support of one communication system to the support of another communication system. For example, it is currently envisioned that a mobile wireless communication device may be designed to move from the support of a cdma2000 1xRTT system to a cdma2000 1xEV-DO system or vice versa. The cdma2000 1xRTT system and cdma2000 1xEV-DO system are also referred to herein as 1xRTT and 1xEV-DO, respectively. The interoperability of a device between 1xRTT networks is the subject of a standard known as TIA/EIA/IS-2001, which is entitled, “Interoperability Specifications (IOS) For cdma2000 Access Network Interfaces.” The interoperability of a device between 1xEV-DO networks is currently the subject of a standard known as TIA/EIA/IS-878, which is entitled, “Inter-Operability Specification (IOS) for High Rate Packet Data (HRPD) Network Access Interfaces.” However, there is no authoritative document describing the interoperability between 1xRTT and 1xEV-DO networks for devices that may support both air interface standards, as this vision of ubiquitous mobility within CDMA standards is relatively recent. When the IS-2000 and IS-856 standards were originally created, full interoperability was not envisioned between such standards, and certain features were deemed optional, rather than required. Hence, various manufacturers and system operators are currently in the predicament of being unable to support seamless transfer of a communication device's PPP session across different CDMA standards, such transfer being confounded by a pre-existing PPP state for the device on the destination network. There is a present need to address this concern.